The XMM-LSS survey. First high redshift galaxy clusters: Relaxed and collapsing systems
Altieri, B.; Valtchanov, I.; Pierre, M.; Willis, J.; Dos Santos, S.; Jones, L.; Andreon, S.; Adami, C.; Bolzonella, M.; Bremer, M.; Duc, P. -A.; Gosset, E.; Jean, C.; Surdej, J.
France, United Kingdom, Chile, Italy, Spain, Belgium
Abstract
We present five newly found galaxy clusters at z>0.6 from the XMM Large-Scale Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the XMM images. For three of them we have sufficient spectroscopically confirmed member galaxies that an estimate of the velocity dispersion is possible: XLSSC 001 at z=0.613 and &sigmaV=867+80-60 km s-1, XLSSC 002 at z=0.772 and σV=524+267-116 km s-1 and XLSSC 003 at z=0.839 and σV= 780+137-75 km s-1. These three clusters have X-ray bolometric luminosities LX ∼ 1-3 × 1044 erg s-1 and temperatures 2-4 keV, and consequently are less massive than previously known clusters at similar redshifts, but nevertheless they follow the low redshift scaling relations between LX, T and σv, within the limits of the measurement errors. One of the clusters, XLSSC 004, is detected independently as an overdensity of galaxies of a colour R-z'=1.4 that matches the redshift of the central galaxy z=0.87, although it cannot unambiguously be confirmed by the spectroscopic observations alone. The highest redshift candidate cluster pertaining to this paper, XLSSC 005, is most likely a double cluster complex at a redshift around unity, associated with an extended X-ray source with probable substructure.
Based on observations obtained with XMM-Newton, CFHT, ESO (program ID: 70.A-0283).